As is generally well known, compressible elastomeric springs are employed in a variety of applications for at least absorbing and dissipating energy from a dynamic impact load applied to the compressible spring. The applied dynamic impact load is due to shock and/or vibration resulting from a specific use of the spring.
Lately, compressible elastomeric springs have been gaining wide acceptance in passenger and freight railcar applications. Specifically, compressible elastomeric springs have been designed for use as an integral part of the side bearing assembly for restricting “hunting” or “rolling” movements of the railcar about a longitudinal centerline. U.S. Pat. No. 7,338,034 issued to Aspengren et al. and U.S. Pat. No. 6,792,871 issued to O'Donnell et al. disclose alternative types of such springs usable in the side bearing assembly.
Of a further importance, compressible elastomeric springs have been frequently employed in railcar buffer assemblies, draft gear assemblies, and drawbar assemblies for cushioning impact energy between two adjoining railcars during make up and operation of a train consist.
For use in applications for at least absorbing and cushioning energy from dynamic impact loads present between a pair of two adjoining railcars, compressible elastomeric springs generally utilize a series of elastomeric pads and metal plate like members arranged in interposed stacked relationship with each other. However, prior to the conception and design of the present invention, the compressible elastomeric springs required guidance during compression and extension movements to provide for lateral stability and satisfactory performance. Generally, such guidance is provided by a metal rod inserted through the central apertures in each pad and plate like member, enclosing the spring into a housing and positioning the edges of the metal plate like members in abutting relationship with the interior wall surfaces of the housing or using a combination of the housing and center rod. However, the use of the housing and/or metal rod increases the manufacturing cost of the initial assembly as well as the maintenance costs during its useful life in railcar operation. Use of housing and/or metal rod also increases weight of the impact energy absorbing assembly. Since there is a continuing desire to increase loading capacity of each railcar, the weight associated with the housing and/or rod adversely affects such loading capacity.
Furthermore, such continuing desire for increased loading capacity adds to dynamic impact loads experienced by the energy absorbing assemblies during operation and makeup of the train consist. Consequently, such higher dynamic impact loads are directly transferred to the compressible elastomeric spring. Moreover, it has been known to exceed mandated maximum speeds during makeup of the train consist which further increases the dynamic impact loads to be absorbed and cushioned by various buffer devices. However, the compressible elastomeric springs presently in use have not been reliable in absorbing all applicable dynamic impact loads. Therefore, there is a continuing need for an inexpensive and reliable compressible elastomeric spring capable of absorbing impact energy loads without the use of the metal rod or the housing for guiding purposes.